Bird arrival dates in Central Europe based on one of the earliest phenological networks

Eva Kolářová*, Peter Adamík

ABSTRACT: Recording arrival dates of migratory birds to their breeding grounds has been one of the most popular activities among naturalists for more than 2 centuries. However, we know extremely little about the timing of birds’ annual cycles when systematic field observations were still in their infancy, before the current warming period. Here we aim at filling this gap for bird arrival dates of 35 species for one of the earliest phenological networks, run by the Bohemian Patriotic-Economic Society during 1828–1847 in the present day Czech Republic. We retrieved station-based archival data and present the arrival dates correlated with local temperature prior to species-specific arrival. The mean slope of arrival advancement with monthly temperature across all species was -1.4 d °C-1 in our study, which is remarkably similar to a recent dataset from the same region. The strength of this relationship depended on species-specific timing of migration. Early migrating species showed stronger negative relationships with temperature than later arriving, long-distance migrants. Cross-correlations in arrival dates among stations were positive and high for well-known species such as skylark, common quail and common cuckoo. Station-based data also showed strong relationships with temperature. For most species, comparisons with recent arrivals (1991-2010) show later arrivals in recent years, and we suggest that changes in population sizes might also play a role in explaining bird phenology.